Needing brake information

moonlitcoyote · September 10, 2019, 04:50 PM

So I have 1 more long trip to make before we call it quits and stop traveling. We need to make it from Colorado to Alabama and so far every time we have been on the road I have had brake issues. We are leaving October 1st so I am hoping to fix "something" before we leave and hope I fix the right thing so I dont have any issues on this last trip.

From what I can remember from our last trip a year ago, the brakes never get hard to push they just seem to not work. It takes a long time to stop. Most of the trip will be great then suddenly it happens and I dont feel like I am going to stop. Last time we stopped at a garage and they were going to change the brake booster but they couldnt get the right part. (at least thats the way I remember it).

Anyway, if I decide to change the brake booster, I have no idea what I am looking for as far as what part. So if someone could help me out there I would appreciate it.

Also if anyone has any idea's of what else might be causing this intermittent problem, I would like to hear it please and thank you.

My Winnebago is a 1985 Chevy P30 with 454 engine. Thank you.

**Edit, after reading back through my old posts it seems that everyone thought I should change the MC again. How do I make sure I get the correct part? After checking autozone for a MC I have 3 options, with JB8 brakes, with JB7 Brakes and with rear disc brakes.

Rickf1985 · September 10, 2019, 06:29 PM

If it were the booster the brakes would get very hard to push. It sounds like you are losing power to the front or rear brakes. I would look at either a master cylinder or proportioning valve if you have one. If you have four wheel disc brakes you probably do not have a prop valve. Do you ever smell hot brake shoes? It is a very distinct smell that and burning clutch are the only things that produce the acrid smell it makes. The booster on my pickup, which was also a hydroboost, would not release fast enough and in heavy traffic it tended to heat the front brakes up so bad that they faded. Have you ever changed all the rubber brake lines?

moonlitcoyote · September 10, 2019, 08:58 PM

I ordered the Master cylinder, should be here tomorrow. I hope I ordered the correct one. This will be the 2nd one I put in since 2015.

I have front disc and rear drum. I know what hot brakes smell like and I have never smelled it on the Winnebago. The issue doesn't tend to happen in heavy traffic. It can happen at times when I haven't even touched the brakes in many miles. I have not changed any brake lines.

Rickf1985 · September 10, 2019, 09:11 PM

Brake hoses may be an issue then. They tend to degrade from the inside and the rubber breaks away and can act just like a valve shutting off the flow if a flap off rubber drops down in the line. At 34 years old I would replace all of the rubber brake lines, they are not all that expensive and it is good insurance.

Froggy1936 · September 11, 2019, 12:22 PM

They are not expensive, But they can be a chore to replace , If you do not have a lift. When i needed one i replaced both , After l/f brake overheated . The one rear one is not too difficult Though bleeding the rears is difficult ,Great to hear you are still operating ! Frank

BrandonMc · September 11, 2019, 12:48 PM

I replaced my lines in the front with the rig on solid ground, no lift required. The rears on mine are solid line all the way to the back, so none were required for the rear. Was very easy all things considered, but I'm young and limber. I then bled the entire system with new fluid using a reverse brake bleeder.

Like rick said, if this is an intermittent issue, I'd personally suspect the lines.

moonlitcoyote · September 11, 2019, 03:37 PM

ok, thanks guys. I am still waiting for the Master cylinder to show up so I will have Eddie get under the rig and check out the lines.

Rickf1985 · September 11, 2019, 04:55 PM

Just a tip, They can look fantastic from the outside, but thirty years of chemicals on the inside is where the damage is done. And Brandon, you have to have a rubber line from the frame to the rear axle to get fluid to the rear brakes and since the axle moves it can't be a solid line. The disc brake vehicles will generally have five rubber lines. One on each caliper and one more from the frame to the rear axle.

moonlitcoyote · September 11, 2019, 08:31 PM

Will have to have Eddie look again because he said the same thing as Brandon. He said the back is all metal.

How would I go about ordering brake lines since they have metal part way and then rubber the rest of the way?

BrandonMc · September 12, 2019, 09:37 AM

Quote from: Rickf1985 on September 11, 2019, 04:55 PM
Just a tip, They can look fantastic from the outside, but thirty years of chemicals on the inside is where the damage is done. And Brandon, you have to have a rubber line from the frame to the rear axle to get fluid to the rear brakes and since the axle moves it can't be a solid line. The disc brake vehicles will generally have five rubber lines. One on each caliper and one more from the frame to the rear axle.

hmmmm I'll need to check that then! thanks for the heads up. kinda forgot about it

Rickf1985 · September 12, 2019, 10:06 AM

You would be looking for brake hoses. Here you go, I think you said before you had disc all around? So you would want R/F, L/F, R/R/ L/R and center rear

https://www.partsgeek.com/catalog/1985/chevrolet/p30/brake/brake_hose.html

Since a lot of it is marked not for motor home you have to go towards the bottom of the list. But the best thing to do is call. If this place does not have a number find one that does. and knowing what brake system you have will definitely help but if all you can tell them id=s disc all around or disc front and drum rear that will help. If you have drums they might have to know the drum size, do you have any receipts from when you did brakes before?

moonlitcoyote · September 12, 2019, 10:37 AM

I dont have any receipts, and I have disk front and drum rear. I looked them up at O'reilly.com and they dont sell anything for the rear. If I'm going to change any brake lines I want to do it at the same time as the M/C. I am assuming I have JB8 brakes, I bought the M/C for JB8 so I hope I am correct in that assumption.

I only have 2.5 weeks left before we leave so I need to make decisions and get things done rather quickly.

DaveVA78Chieftain · September 12, 2019, 02:41 PM

There are 3 possible brake configurations and I read threads about all 3 possibilities
JB7 - Vacuum booster with Front Disk/Rear Drum
JB8 - Hydroboost Booster with Front Disk/Rear Drum
JF9 - Hydroboost Booster with 4 Wheel Disk

NAPA carries most all parts

Rickf1985 · September 12, 2019, 03:23 PM

Well you got the one for the front disc and rear drum, do you have the hydroboost booster? It will have hydraulic lines running to it from the power steering pump.

moonlitcoyote · September 13, 2019, 12:22 PM

I'm not EXACTLY sure what a hydroboost booster is, but I think it's what I have. I got the 2 front brake lines and the M/C so I hope that fixes the problem. Installing them today.

Rickf1985 · September 13, 2019, 04:28 PM

I am hoping it was the master cylinder because if it was a failing line it was probably the rear line since you did not mention it pulling hard to one side or the other which would happen if it were a front line. And I should be saying "hose" instead of line.

Hydroboost has three hydraulic lines on it and the master cylinder attaches to that. Vacuum booster is a large round can and booster attaches to that. If you ever had to stomp on the brakes hard and fast and you felt the steering wheel feel dead for a second then you have hydroboost. Plus with hydroboost if you stomp on the brakes hard the pedal will go down and push back up quickly.

DaveVA78Chieftain · September 14, 2019, 12:15 AM

Master Cylinder attaches to the booster unit

JB7 Vacuum Booster operates off of engine vacuum (top pic)
JB8/JF9 Hydroboost unit runs off of the Power Steering pump (bottom pic)

Rickf1985 · September 14, 2019, 09:25 AM

Yup, Pictures do make it a lot easier.

moonlitcoyote · September 14, 2019, 06:49 PM

Thank you Dave, I dont have the Vacuum boost, mine is not big and round. Also Eddie swears there are NO rubber lines to the rear brakes.

BUT now we have a HUGE problem. We changed the M/C and the front brake lines. We bled the M/C before we put it in but now we cant get the rear bleeders undone. No wrench seems to fit it and we cant reach it with anything else. Is there ANY possible way to bleed these without using the bleeder valve?

I dont know what to do, can we skip bleeding 1 of the rear wheels?

Froggy1936 · September 14, 2019, 08:49 PM

Hi MJ There is a very special wrentch made to fit on the rear bleeders (due to the small space between the spring and the backing plate) But if you cannot obtain one you can open The fitting to the wheel cly enough for fluid/air to get out This will bleed all but the cly Frank .

moonlitcoyote · September 14, 2019, 09:21 PM

I tried that but it looked and felt like I might break the line, the swivel part that screws in, wasn't swiveling. I am so lost at this point.

Rickf1985 · September 15, 2019, 10:47 AM

The fitting on the rear wheel cylinder is either 10 mm metric or 3/8 SEA, I have seen both and I had to make my own wrench to fit using a standard wrench and heating and bending till it fit where I needed it to go. As Frank said, You can bleed it where the line goes into the wheel cylinder but if any air gets in the cylinder you will not be able to get it out that way. sometimes heating the fitting with a propane torch will release it but you are going to boil the fluid and then you will have air to deal with for sure. I know you do not want to hear this but what I have had to do on many occasions when dealing with this on trucks is you have to take the wheels off so you can get in there and get access from the top. As far as that rubber line on the rear it will be close to the center of the rear differential. Both metal lines from the rear brakes will come together at a fitting which may or may not be part of the rubber line going up to the frame. Look for the differential vent sticking up our of the differential since this is usually what is used to bolt the hose fitting down.

moonlitcoyote · September 16, 2019, 05:18 PM

We ended up breaking one of the rear lines trying to get the bleeder valve out. So, we put in a new m/c, new brakes lines on the front and 1 new line on the rear along with the new bleeder valve. Just finished bleeding them. If i still have problems with the brakes after this .....

Rickf1985 · September 16, 2019, 07:38 PM

If you put one new line on the rear then you found the rubber line. Did you turn in the master cylinder you took out for a core? I am really hoping the answer will be no because that will mean you bought a brand NEW one and not a rebuilt. I am also curious to see the piston from the old one if you still have it. It sounds like the rear piston cup was folding over intermittently. I say the rear because you said you still had brakes but not as much as you should which would sound like lost rear brakes. front brakes do 70% of the stopping and if you lose them you know it, RIGHT NOW do you know it!!!!! You might as well have no brakes at all if you are doing 50 MPH.

While we are on the brake subject and you are going on a trip, Do your emergency brakes go to the rear wheels or the driveshaft behind the transmission? If behind the rear wheels be sure to back off on the starwheels for the brake adjustment a few clicks and then adjust up the emergency brakes until they are just touching and then just barely back them off and after that readjust your service brake up to the just touching point. This is a procedure that is done wrong on just about every drum brake equipped vehicle I have ever worked on. Once set up right the owners are amazed at how much better the brakes feel. That is because the rear rake are now actually working.